Process for forming artificial teeth



Oct. 22, 1946. M. 's." MOSKEY 2,409,783

PROCESS FOR FORMING ARTIFICIAL TEETH Original Filed March 20'. 1942 2Sheets-Sheet l llq'g INVENTOR J MOSKOS 5. MOSKEY V Oct. 22, 19 46." M.SQMOSKEY 2,409,783

- PROCESS FOR FORMING ARTIFICIAL TEETH Original Filed larch 2d. 1942 2sheets 'sheet INVENTOR.

' MosKuss. MOSKEY Patented Oct. 22, 1946 UNITED STATES PATENT OFFICEPROCESS FOR FORMING ARTIFICIAL TEETH Moskos S Moskey, Lakewood, OhioOriginal application March 20, 1942, Serial No.

435,516. Divided and this application July 27, 1944, Serial No. 546,843

This invention relates to dentistry and particularly to the processwherein dental crowns or bridges may be reproduced with a perfection andan exactness heretofore not attainable and which artificialreproductions simulate natural mould to the center of the hollowthereof. -In

other words, the artificial member was constructed in stages which werein reverse of a logical order of assembly or development. elucidate thispoint, attention is called to the fact that the prior art moulds dividedthe tooth member longitudinally in two parts; that is, the labial sidewas formed in one-half of the mould, the lingual side was formed in theother half and the two halves were joined together. Therefore, byfilling each half separately in that manner the material was appliedfrom the visible outer surface of the artificial member inwardly to theinvisible. central mass thereof. By these earlier methods, it was notpossible to see how the surface of the tooth would finally appear beforeit was finished. The technician could only guess as to the final outcomefor. the reason that he could not get a proper view of the outersurfaceof the article during its build-up before it was completed. 1

None of the earlier inventions permitted the technician to work on theartificial member at different stages of its curing or setting period.This necessitated, at the beginning of the manufacture, the insertion ofvarious colored slips of plastic pieces to cause the ultimate simulationof natural tooth stains, cracks or similar blemishes. The outcome ofsuch procedure is highly speculative and the percentage of rejections ordis-- cards is quite high.

In the earlier art, no attempts were made to faithfully reproduce thelingual side of the tooth to the same degree as the labial side wasreproduced The prior devices and technique do'not make possible thecommercial reproduction of the lingual side of the tooth, with theresult that the lingual side had by contrasta distinctly artificialappearance; .7

To further 6 Claims. (c1. 18-551) One object of this invention is toprovide asystematic process for the packing of such flask and mouldtherein withplastic materials or acrylics which accomplish theaforementioned result.

A further object of this invention is to provide a method for buildingup artificial teeth in certain steps or stages so that all of theoptical characteristics of a natural tooth may be better reproduced.

A still further object is to permit the construction or gradual build-upin a multi-part mould of an artificial tooth or other article from theinner central mass to the outer exposed surface thereof.

These and other objects and features of the invention will becomeapparent from a study of the following description and claims togetherwith the accompanying drawings in which like 7 parts are designated bylike reference characters and wherein:

Figure l is an expanded perspective view of a flask made in accordancewith this invention; Figure 2 is a longitudinal cross-section of themiddle element of the flask shown in Figure 1; Figure 3 is a lateralcross-section of the same element of the aforesaid flask;

Figure 4 is an expanded perspective view of the wax model, the platinumcap and the amalgam matrix used in the process for reproducing a dentalcrown;

Figure 5 is a vertical cross-section of the above mentioned wax modelalone;

Figure 6 is a plan view of the bottom tray of the flask with lingualimpression or matrix therein;

Figure 7 is a top plan'view of the intermediate section of the sameflask with the wax model therein and particularly showing the labialside or part thereof;

Figure 8 is a bottom view of the intermediate section of the same flaskshowing the lingual side of the wax model therein;

Figure 9 is a plan view of the top tray of the same flask inverted andshowing labial impression or matrix therein;

Figure 10 is a vertical lateral cross-section of combined bottom trayand intermediate section showing the wax model, the platinum cap and theguide pin used for supporting the model and cap in the soft investmentmaterial, the view being a section along the line and in the directionof the arrows I0 I 0 of the Figure '7;

Figure 11 is a vertical cross-sectional view of the mould partlyexpanded with wax model reawe ice 3 moved and just showing the platinumcap and the aforesaid guide pin;

Figure 12 is a perspective view of the bottom tray and the intermediatesection assembled with a sheet of wet Cellophane therebetween and readyfor packing the labial side of the crown;

Figure 13 is a perspective view of the top tray and the intermediatesection assembled with a sheet of wet Cellophane therebetween and readyfor packing the lingual side of the crown; and

Figure 14 is an enlarged vertical sectional view of a finished specimencrown showing the blended materials in the lingual, the labial and theintermediate parts of the crown and particularly in the gingival, medialand incisal parts thereof.

In the drawings and particularly in Figures 1,

2 and 3 thereof, there is illustrated a metal flask composed of threeprimary elements. There is, first, the drag or bottom tray 25; second,the cope or inverted top tray 30, and lastly the intermediate or middlesection 43. Each of these parts will be described in detail and in theorder just set forth.

The bottom tray 23 is a rather substantial metal piece which has a flatbottom part 25 and from which there extends upwardly two end walls 2|and the two side walls 22 forming a rectangular pan or tray-like member.Each of the two side walls 22 have extension wall portions 23 thereonwhich have curved top edges. Each of the end walls 21 is provided with avertical hole 24 which receives a certain connecting pin 44 here inafterdescribed. The bottom tray 23 may be for most purposes approximatelythree inches lon and about two inches wide and should be of a heavydurable construction in order to withstand the pressure applied theretowhen the assembled flask is subsequently put into a press or betweensuitable clamps.

The top or inverted tray 35 is substantially the same as the bottom tray20. It too has a top portion 25 from which there depend two end wallsand two curved side walls 42 connected-together to form an openrectangular frame. The side walls 42 are, however, curved. The loweredges thereof are recessed to snugly engage the raised extensions 23 ofthe bottom tray member and the top edges thereof are raised to fit therecessed portions 33 of the inverted tray member. Each of the end Walls4| is provided with a pair of extending and a pair of depending alignedpins 44 which-pins engage the holes 24 and 34 of the aforesaid bottomand top trays and 30 respectively in the manner shown in the drawings.

The two end walls 4| and one of the side walls 42 of the middle section40 are provided with inwardly extending portions referred to herein asflanges 55 and 46. The flanges 46 on the two end walls are attachedthereto at about the middle of the wall and extend laterally inwardlyand upwardly at an angle which approximately corresponds to thecurvature of the adjacent side walls 42. The flange 45-which is on theside wall 43 is curved longitudinally to correspond with the curvatureof the side wall, extends inwardly a short distance and joins the twoflanges 45.

The opposite curved side wall 42, the one that does not have a flangethereon, is provided with a small lateral hole 43 which will receive asmall dowel or guide pin 48 hereinafter mentioned. This hole 43 issubstantially in line with the aforesaid flange 45 on the side wall 43.

The aforesaid top tray and section 30 and 49, like the bottom tray 28,are substantially made of durable material and when assembled completelyregister and are able to receive a considerable pressure in a clam orpress, and also, when so assembled, form a closed box-like structure.

The center section of the flask in which the wax pattern is invested, isin reality an open frame which permits the operator to apply thegingival, middle third and incisal plastic as precisely as though thecase were mounted upon an open model. The outside sections of the flaskare used only for compression and as a lingual and labial counter-die toregister and mould the material to the desired form.

For the purpose of quickly identifying the parts of each flask and sothat the sections may be fitted together easily and in their properorder, each section is marked with indicia, such as by the letter Tindicated by the characters 29, 39 and 49 of the respective elements 25,30 and 40. These identification marks 29, 39 and 49 appear only once oneach section of the flask and when the sections are assembled so thatthe marks appear in an ordinary arrangement, such as one above theother, the technician instantly knows that the moulds are in properorder. This marking is important, particularly when many flasks areused, as the time usually taken to examine each part to see that it fitsproperly and to try each section to see that the parts of the mould arerelated is saved.

The technique The technique of preparing the tooth model for the hereindescribed flask and process is substantially the same as the preparationof the model for a conventional porcelain crown. That is, a stone or anamalgam die 5i having a model 52 of the natural tooth stump thereon isprepared, over which there is swaged a platinum matrix 53 having wallsof about one-thousandth of an inch thick. A small shoulder should beformed on the portion of the matrix 53 which will be adjacent to thegingival portion 54 of the artificial tooth or crown. The wax model 55and the matrix 53 together, as shown in the Figure 5, are removed fromthe die 5| and are inserted in the flask, as directed in the followingprocedure.

In the process of making the mould, a mixture of powdered stone, plasterand water is prepared which has a thicker-'than-cream consistency. Thismixture is hereinafter referred to as the investment, and is indicatedby the reference character 41 when used in the middle section 40, by thecharacter 21 when used in the bottom or convex tray 20, and by 31 whenused in the top or concave tray 30. The matrix 53 is filled with some"of the plastic investment 41 and is set aside temporarily until itbecomes stiffer but not quite solid. A small piece of wire or a nail,herein called a guide pin 48, is inserted through the opening 43 in theside wall 42 of the middle section of the flask. If more than one toothis to be processed, then a separate guide pin 48 should amazes beinserted for each tooth. While the drawings show'only one hole 43 in theside wall 42, it should be understood that many more may be drilled ifthe nature of thework requires them. i The middle section of the mouldis prepared first. The investment 41 is built up fromthe side wall 42having the hole therein for the removable pin 48. The investment tapersinward and stops at a point a little short of the inner endof the pin 48or to about where the gingival edge of the crown will come. The waxmodel 55 of the tooth is then mounted on the inner end of the pin 48 sothat it is approximately in the centerofithe section and sothatthelingual side 58of the tooth model faces the concave side of thesection; The wax model 55 is held in place on the end of the pin by thestill plastic investment in the matrix 53 and also by the investmentbuilt up'from the wallthat adheres to the small flange orshoulder 54 ofthe-matrix. r i i Other investment material..41 is then used to fill thesection and to neatly encircle the wax model 55. The material tapersinward from the two ends andthe other side Walls and is supported whileplastic thereon by the flanges 45 and 46 of the section. The investment41 touches the model 55 at the peripheral edge thereof only. Theinvestment tapers sharply from the walls as is shown in the Figure10,and.only a very narrow frame of the material is formed around thelargest circumference of the model. The portion of the crown adjacent toor contacted by the investment 41, which portion includes the incisaland sides, is hereinafter referred to as the medial portion and isindicated in the Figure 14 by the character I54. The investment 41 isallowed to set'and thoroughly harden.

After the investment 41 has set, a separating medium such assodi'umsilicate is applied to both sides thereof. Next, a little of the fresh,softrinvestment material 21 is carefully painted or spread over theexposed lingual surface 58 of the wax model and over the investment 41adjacent thereto which was previously coated with the separating medium.I A fresh relatively soft investment is preferably used in order toinsure an accurate reproduction of the model. i

The bottom tray 20 is then filled with some material 21 which has aslightly thicker consistency and the section 40 and tray. 20 areassembled.

.Similarly a small amount of thin investment is spread on the labialsurface 51 of the. modeland over some of the treated investment adjacentthereto. The top tray 30 is also filled withsome of the thicker.investment 31; and then. placed on the section 40. The assembled flasksections 20, 30 and 40 are pressed togetherso that all excess investmentmaterial 21 and 31 is allowed to come out and so that an accurateimpressionof both sides of the model is obtained. The closed andassembled flask is then allowed to set until the investments 21 and 31in the top and bottom trays have completely hardened. At this, stage,better results are obtained if the flask is pressed or the 58 of thetooth. The depression formed in the top member 30 is the mould for thelabial side 51 of the tooth. In the Figure 11, this labial mould isindicated by the reference character 58a. The narrow band or frame inthe center of the middle section 40 which formerly touched theperipheral edge or circumference of the wax model' 55 is now the mouldfor the thin contour I54 of the tooth and is that portion of the entiremould between the lingual and labial moulds. This then leaves theplatinum matrix 53 exposed in the opening 55a of the section 40. Featheredges and rough spots on the investments 21, 31 and41 are carefullycarvedaway and the pattern is gently smoothed out in the conventionalmanner.-w

If desired, a thin coat of very transparent resin maybe applied to thelingual and labial surfaces of the crown as indicated in Figure 14 bythe characters I55 and I56. This is like the thin enamel coating on anatural tooth and tends to create an optical effect which has a veryrealistic appearance.

, In the process of making the mould from th Wax model, it is immaterialwhich of the trays 20 or 30 is made first. As the process was justdescribed, the bottom tray 20 with the lingual mould was set forth firstbut it should be obvious that the labial mould could be preparedimmediately afterthe preparation of the middle sec tion. Also, it shouldbe noted that the two trays 20 and 30, with their respective lingual andlabial moulds, could be prepared simultaneously.

The next broad step consists of packingthe acrylic mould formed by thehardened investment materials 21, 31 and 41. However, before packing themould with the thermoplastic or thermo-settingmaterial, whichever isused to form the ultimate artificial toothor crown, the walls and edgesof the mould should be painted with more thin sodium silicate to assuremaximum smoothness, hardness and strength thereof. Thisthermoplastic orthermo-setting material of which the crown is to be made is referred tohereinafter simply as resin. When the sodium silicate coat isdry, apiece of moistened Cellophane 6| is then placed between the lingualsection or tray 20 of the flask and the middle section .40 thereof, asshown in the Figure 12. This leaves thelabial and the middle portions ofthe mould exposed for packing- The Cellophane film is used to preventadhesion of the plastic resin to the lingual mould. First, the labialside of the platinum matrix 53 is covered with plastic resin I55. Thismay be anuQDaque :resin of suitable color and shade. Second, the resinI51a is applied over the resin I55 near-thegingivaledge. This resin maybe a little more transparent than theresin I55 and its shade may beaffected by the underlying resin I55. Third,;'the resin I51b is appliedover the other resins I55 and I51a. This likewise may be a little moretransparent than the former two resins. -Next,- the resin I51c isapplied over the other three. This last resin I51c is more transparentthan the others. I

The resins should be properlytinted and have the required degrees.oftransparency so that the finished crown will have an appearance ofdepth and solidity. Each layer of resin 151a, I51b and I510 should betapered so thattthe colors and shades blend into each other naturally tocreate the appearance of a real tooth. 1

At this" stage, theouter surface of; the crown is roughand crude. yet ithasqnotbeenimof resin applied are only estimated as cient to fill thelabial mould. 1

After the material has been applied labially as aforesaid, a secondpiece of dampened Cellophane 62 is placed onthe surface of the labialsection or. inverted .-tray 39 of the .fiask andthe middle section 40and the bottom tray 20 are placed over it, using finger pressureonly tobring the sections together. The bottom tray 20 or lingual section isremoved together with the Cellophane 61, thus exposing the lingualportion .of the mould. for

packing.

The lingual area is then packed inthe same manner as the labialj. thatis,.xthe resins l58a, I581) and 1580 are laid and blended as needed, except that a little more material is used to obtain greater bulk and sothat bettercompression of the materials is obtained. 1 Upon completionof the packing, the dampened Cellophane 6| is again applied to thelingual section of the flask as aforesaid. The three parts of the fiaskare then assembled and locked in a portable clamp and prepared for atest pack. The clamped flask is then placed in boiling water for aboutthree minutes or for a duration of time which partially cures the resinand is then opened for corrections. Excess material may be removed fromthe lingual side. Special stains or coloring may then be applied to theexposed lingual and labial surfaces of the unfinished crown. The middlesection may be held up to the light orheld near a darkened cavitypractically simulating an oralcavity so that the translucency of theincisal edge may be checked. If desired, the entire incisal may be cutout and repacked with a more or less translucent mix if heeded.Repacking, however, should be done from the labial side first andfollowing the same procedure as described above. Next, moist Cellophaneis placed between the sections and the flask is tightly closed with fullcompression in a suitable clamp or press. The plastic resin is cured forat least one hour, after which it should be thoroughly cooled in coldwater before being opened. v

, After the flask sections 20, 30 and 40 are opened and separated, theguide pin 48 is removed from the middle section. This may be easily donewith a pair of pliers. The investment material 41 is carefully brokenaway-from around the circumbeing Suffi-v ference of the crown, Theplatinum matrix 53 is peeled from inside the recess 56 of'the crown sothat it may be set up on the original die for finishing and polishing inthe conventional man- For the purpose of simplicity, the'technique'asdescribed and illustrated herein is for a simple jacket crown. However,it should be understood that bridges and other types of artificial teethmay be constructed in much the same manner. Persons skilled in the artmay readily adapt the foregoing technique to that of the preparation ofbridges, for example. However, it has been found that in the caseofbridge work, best results are obtained if a proper reinforcing barisused to connect whatever abutments are 'used'in thecase.

In bridgework involving two or more teeth, the reinforcing bar should bepositioned midway between the tissue and incisal and should be shaped toconform with the contour of the gum line. After'the bar is soldered tothe abutments, the skeleton isplaced on the model'and the wax dummy iscarved. The wax form may thenbe removed and tried in the mouth for biteand fit and when found satisfactory, the wax bridge form invested in theflask in the same way as for the single jacket crown heretoforedescribed, using as many uide pins teas are necessary to hold it inplace while the investment material is packed around it. The labial andlingual sides of .the pattern are thus exposed the same Way,

It will now be clear that there is provided by this invention a processfor forming artificial teeth which accomplishes the objects set forthherein. While. the invention has been disclosed in its preferred form,it is to be understood that the embodiment thereof as described andillustrated is not to beconsidered in a limited sense as there may beother forms or modifications of the invention which should also beconsidered to be within the scope. of the appended claims.

I claim:

1. The method of forming an artificial tooth, comprising, first, forminga separable three-piece mould of the tooth;to be formed, the first pieceof the mould having the impression of the labial portion, the second.piece having the impression of the lingual portion and the middle piecehaving the impression of the medial portion of the tooth; second,assembling the second and middle pieces of the mould and roughly packingtherein the material forming the lingual portion of the tooth; third,assembling the first and middle pieces of the mould and roughly packingtherein and on the aforesaid material other material forming the labialportion of the tooth; and fourth, assembling the first, second andmiddle pieces of the mould and finally moulding and forming the completetooth therein with the aforesaid roughly packed materials.

2. The method of forming an artificial tooth, comprising, first, forminga separable three-piece mould of the tooth to be formed, the first pieceof the mould having the impression of the labial portion, the secondpiece having the impression of the lingual portion and the middle piecehaving the impression of the medial portion of the tooth; second,assembling the second and middle pieces of the mould and roughly packingand blending therein materials of different shades and difierent degressof transparency, thus forming the lingual portion of the tooth; third,assembling the first and middle pieces of the mould and roughly packingtherein and on the aforesaid materials other material forming the labialportion of the tooth; and fourth, assembling the first, second andmiddle pieces of the mould and finally moulding and forming the completetooth therein With- -the aforesaidroughly packed materialsw f1 a 3. Themethod'of forming an artificial tooth, comprising, first, forming aseparable three-piece mould of the tooth to be formed, the first pieceof the mould having the impression of the labial portion, the secondpiece having the impression of the lingual portion and the middle piecehaving the impression of the medial portion of the tooth; second,assembling the second and middle pieces of the mould and roughly packingand blending therein materials of different shades and different degressof transparency, thus forming the lingual portion of the tooth; third,assembling the-first and middle pieces of the mould and roughly packingand blending therein and on'the aforesaid materials other materials ofdifferent shades and different degrees of opacity, thus forming thelabial portion of the tooth; and fourth, assembling the first, secondand middle pieces of the mould and finally moulding and forming thecomplete tooth therein with-the aforesaid roughly packed. materials.

4. The method of forming an artificial tooth, comprising, first, forminga separable three-piece mould of the tooth to be formed, the first pieceof the mould having the impression of the labial portion, the secondpiece havingthe impression of the lingual portion and the middle'piecehaving the impression of the medial portion of the tooth; second,assembling the second and middle ieces of the mould and roughly packingtherein the material forming the lingual portion of the tooth; third,assembling the first and middle pieces of the mould and roughly packingtherein and on the aforesaid material other material forming the labialportion of the tooth; fourth, assembling the first, second and middlepieces of the mould and moulding the complete tooth therein with theaforesaid roughly packed materials; fifth, removing the first piece ofthe mould and staining the material exposed thereby to simulate naturalblemishes; and sixth, reassembling all of the pieces of the mould andcuring the material therein to form a finished artificial tooth.

5. The method of forming an artificial tooth, comprising, first, forminga separable three-piece mould of the tooth to be formed, the first pieceof the mould having the impression of the labial portion, the secondpiece having .the impression of the lingual portion and the middle piecehaving the impression of the medial portion of the tooth; second,assembling the second and middle pieces of the mould and roughly packingand blending therein materials of different shades and different degreesof transparency, thus forming the lingual portion of the tooth; third,assembling the first and middle pieces of the mould and roughly packingand blending therein and on the aforesaid materials other materials ofdifferent shades and different degrees of opacity, thus forming thelabial portion of the tooth; fourth, assembling the first, second andmiddle pieces of the mould and moulding the complete tooth therein withthe aforesaid roughly packed materials; fif-th, removing the first pieceof the mould and staining the material exposed thereby to simulatenatural blemishes; and sixth, reassembling all of the pieces of themould and curing the material therein to form a finished artificialtooth.

6. The method of forming an artificial tooth, comprising, first, forminga separable three-piece mould of the tooth to be formed, the first pieceof the mould having the impression of the labial portion, the secondpiece having the impression of the lingual portion and the middle piecehaving the impression of the medial portion of the tooth; second,coating the lingual and labial surfaces of the labial and lingualportion of the mold pieces with a thin transparent resin; third,assembling the second and middle pieces of the mould and roughly packingtherein the material forming the labial portion of the tooth; fourth,assembling the first and middle pieces of the mould and roughly packingtherein and on the aforesaid material other material forming the lingualportion of the tooth; fifth, assembling the first, second and middlepieces of the mould and then moulding and setting the complete tooththerein of the aforesaid roughly packed material.

MOSKOS S. MOSKEY.

